The Stovebolt Site Forums The Shop Area Engine Shop Ballast resistor

So your starter solenoid will have 3 studs to attach wires.

A big stud for the battery cable.

A small stud (usually marked "S") that comes from the start position on the ignition switch. When activated, it causes the starter solenoid to pull in, engaging the starter drive gear to the flywheel and at the same time supplying power to cause the starter motor to spin.

Another small stud (usually marked "R") which passes battery voltage down the attached wire directly to the + terminal on the coil. This "bypasses" the external ballast resistor, supplying full battery voltage to coil + while starting the engine.

But before doing anything you need to find out if your coil has an internal resistor.